Language Server

This appendix details the installation and configuration of furiosa-rust-analyzer-proxy, a proxy for rust-analyzer that provides IDE support for mapping expressions. The proxy runs rust-analyzer underneath, forwards normal Rust language-server traffic to it, and rewrites editor-facing results so mapping types are displayed in m![...] notation.

Installation

1. Ensure rust-analyzer is installed and available in your PATH. The proxy launches this upstream rust-analyzer process to provide standard Rust IDE features.

2. Download the furiosa-rust-analyzer-proxy binary from the GitHub releases and make it executable:

   curl -L -o furiosa-rust-analyzer-proxy \
     https://github.com/furiosa-ai/furiosa-opt/releases/latest/download/furiosa-rust-analyzer-proxy-x86_64-unknown-linux-gnu
   chmod +x furiosa-rust-analyzer-proxy
   

3. Configure your IDE to use the downloaded binary instead of the default language server. For example, in VSCode, update your settings.json:

   {
     "rust-analyzer.server.path": "/path/to/furiosa-rust-analyzer-proxy",
     "rust-analyzer.inlayHints.maxLength": null  // recommended to reduce '_' truncation
   }
   

Environment variables

You can configure the language server using environment variables. For example, in VSCode, update your settings.json:

{
  "rust-analyzer.server.extraEnv": {
    "ENV_NAME": "env_value"
  }
}

• FURIOSA_RUST_ANALYZER_PROXY_UPSTREAM: Custom path to the upstream rust-analyzer binary that the proxy launches. Defaults to rust-analyzer in PATH.

Features

The proxy delegates standard Rust IDE features to rust-analyzer and rewrites mapping expressions in editor-facing results.

Call Hierarchy

Provides incoming and outgoing call hierarchy views. Function details shown in hierarchy entries are converted into mapping expressions.

Code Actions

Provides quick fixes, refactors, and other editor actions. Action title and text edits are converted into mapping expressions.

Code Completions

Provides completion items for names, methods, functions, types, and snippets. Completion labels, detail text, and text edits are converted into mapping expressions.

Diagnostics

Provides diagnostics from rust-analyzer and rustc. Diagnostic messages and related information are converted into mapping expressions.

Hover

Shows additional information when hovering over a symbol. Hover contents such as inferred types, function signatures, and documentation are converted into mapping expressions.

Inlay Hints

Shows additional information inline with the source code. Inlay hints are converted into mapping expressions.

Tip

For the most accurate conversion, set rust-analyzer.inlayHints.maxLength to null (unlimited length). This reduces how often long inlay hints are truncated into ‘_’.

Signature Help

Shows function signatures and the active parameter while writing a call. Signature labels, parameter labels, and documentation are rewritten to use mapping notation, including offset-based parameter labels returned by LSP clients.

Caveats

The language server may incorrectly interpret user-defined types as mapping expressions if they share names with internal mapping components. For instance, if you define a custom Symbol<T> struct, the language server might mistakenly display it as m![T] in your IDE. This is purely a UI display issue and does not affect the other LSP behaviors.